Modern computing and display technologies have facilitated the development of systems for so-called “virtual reality” or “augmented reality” experiences, wherein digitally reproduced images or portions thereof are presented to a user in a manner where they seem to be, or may be perceived as, real. A virtual reality (VR) scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input, whereas an augmented reality (AR) scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user.
For example, referring to FIG. 1, an augmented reality scene 2 is depicted wherein a user of AR technology sees a real-world park-like setting 4 featuring people 6, trees 8, buildings 10, and sky 12 in the background, and a concrete platform 14. In addition to these items, the user of the AR technology also perceives that he “sees” a robot 16 standing upon the real-world platform 14, and a cartoon-like avatar character 18 flying by which seems to be a personification of a bumble bee, even though these elements 16, 18 do not exist in the real world. As it turns out, the human visual perception system is very complex, and producing a VR or AR technology that facilitates a comfortable, natural-feeling, rich presentation of virtual image elements amongst other virtual or real-world imagery elements is challenging.
VR and AR display systems can benefit from information regarding the head pose of a viewer or user (i.e., the orientation and/or location of user's head).
For instance, head-worn displays (or helmet-mounted displays, or smart glasses) are at least loosely coupled to a user's head, and thus move when the user's head moves. If the user's head motions are detected by the display system, the data being displayed can be updated to take the change in head pose into account.
As an example, if a user wearing a head-worn display views a virtual representation of a three-dimensional (3D) object on the display and walks around the area where the 3D object appears, that 3D object can be re-rendered for each viewpoint, giving the user the perception that he or she is walking around an object that occupies real space. If the head-worn display is used to present multiple objects within a virtual space (for instance, a rich virtual world), measurements of head pose can be used to re-render the scene to match the user's dynamically changing head location and orientation and provide an increased sense of immersion in the virtual space.
Head-worn displays that enable AR (i.e., the concurrent viewing of real and virtual elements) can have several different types of configurations. In one such configuration, often referred to as a “video see-through” display, a camera captures elements of a real scene, a computing system superimposes virtual elements onto the captured real scene, and a non-transparent display presents the composite image to the eyes. Another configuration is often referred to as an “optical see-through” display, in which the user can see through transparent (or semi-transparent) elements in the display system to view directly the light from real objects in the environment. The transparent element, often referred to as a “combiner,” superimposes light from the display over the user's view of the real world.
Most pertinent to the present inventions is the optical see-through AR display, which allows the user to directly view ambient light from the real-world environment. In general, it is desirable that the virtual objects that are superimposed over the real world be opaque, so that real objects or portions thereof behind the virtual objects from the user's perspective are completely obscured to provide a real world experience to the user. However, because the light from the real world is combined with the light from the virtual world, as opposed to being blocked by the virtual world, the virtual objects or portions thereof may appear transparent or translucent when overlapping real objects.
There, thus, is a need to ensure that virtual objects displayed to a user in optical see-through AR system are as opaque as possible.